Capacitive digital to analog and analog to digital converters

ABSTRACT

A digital-to-analog converter (DAC) comprises a capacitive DAC that comprises N first capacitances that are connected in parallel and that have first ends and second ends, wherein N is an integer greater than one, and N first switches that selectively connect a selected one of the second ends of the N first capacitances to a common node and non-selected ones of the second ends of the N first capacitances to one of a voltage potential and a reference potential. Capacitance values of the N first capacitances are substantially equal. A second DAC communicates with the common node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/715,078, filed on Sep. 8, 2005, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to digital to analog (D/A) and analog todigital (A/D) converters, and more particularly to capacitive and/orresistive D/A and A/D converters.

BACKGROUND OF THE INVENTION

Digital to analog (D/A) converters can include arrays of capacitors thatare selectively switched to convert a digital signal to an analogcounterpart. However, mismatch between capacitors may cause the D/Aconverter to be non-monotonic. Monotonicity in a D/A converter meansthat as the digital input to the converter increases over a full-scalerange, the analog output never exhibits a decrease between oneconversion step and a subsequent conversion step. In other words, theslope of the transfer characteristic is never negative in a monotonicconverter.

Referring now to FIG. 1A, a D/A converter 10 is shown. The D/A converter10 includes a binary capacitor array 14, switches 16 and 18, anoperational amplifier (opamp) 20, and a capacitor C_(f) in a feedbackarrangement with the opamp 20. Each of the capacitors in the array 14have different values. More particularly, each capacitor in the array 14is twice the value of the preceding capacitor. Switches SW selectivelyswitch the capacitors in the array 14 between a voltage reference and areference potential such as ground.

In use, the D/A converter 10 has sampling and integration stages. In thesampling stage, the switch 16 closes and selective ones of thecapacitors are charged to the voltage reference as determined by theswitches. In the integrating phase, the switch 16 is opened and theanalog output is generated. For example, a four bit array may close afirst or most significant bit (MSB) switch and a least significant bit(LSB) switch to represent 9/16 of a voltage reference.

Referring now to FIG. 1B, a non-monotonic output of a D/A converter isshown. For example, the analog output exhibits a decrease from oneconversion step to the subsequent conversion step as shown at in FIG. 1Bat 44. The non-monotonic output may be due to capacitor mismatch. Forexample, the capacitor 2^(N-1)C may be different than 2^(N-2)C+2^(N-3)C+. . . +2C+C. Ideally, 2^(N-1)C−(2^(N-2)C+2^(N-3)C+ . . . +2C+C)=C. Inother words, the difference between the MSB capacitor and the rest ofthe capacitors should be equal to a smallest or LSB capacitor

Referring now to FIG. 2, a D/A converter 50 including a linear capacitorarray 54 is shown. The linear capacitor array 54 includes 2^(N)-1capacitors that are selectively switched between a voltage reference andreference potential such as ground. While the linear capacitor array 54inherently monotonic, the number of switches required growsexponentially with the bit resolution. For example, a 16-bit digital toanalog converter includes 2¹⁶-1 pairs of switches, which may beimpractical.

SUMMARY OF THE INVENTION

A digital-to-analog converter (DAC) comprises a capacitive DAC thatcomprises N first capacitances that are connected in parallel and thathave first ends and second ends, wherein N is an integer greater thanone, and N first switches that selectively connect a selected one of thesecond ends of the N first capacitances to a common node andnon-selected ones of the second ends of the N first capacitances to oneof a voltage potential and a reference potential. Capacitance values ofthe N first capacitances are substantially equal. A second DACcommunicates with the common node.

A digital-to-analog converter (DAC) comprises first converting means forconverting a digital signal to an analog signal and that comprises Nfirst capacitance means for providing capacitance that are connected inparallel and that have first ends and second ends, wherein N is aninteger greater than one and N first switching means for selectivelyconnecting one of the second ends of the N first capacitance means to acommon node and others of the second ends to one of a voltage potentialand a reference potential. Capacitance values of the N first capacitancemeans are substantially equal. Second converting means converts adigital signal to an analog signal and that communicates with the commonnode.

A method for providing a digital-to-analog converter (DAC) comprisesconnecting N first capacitances of a first capacitive DAC in parallel,wherein the N first capacitances have first ends and second ends, N isan integer greater than one, and capacitance values of the N firstcapacitances are substantially equal. The method includes selectivelyconnecting a selected one of the second ends of the N first capacitancesto a common node; selectively connecting others of the second ends toone of a voltage potential and a reference potential; and connecting asecond DAC to the common node.

A pipelined analog-to-digital converter (ADC) comprises a first stagethat receives an input voltage signal and that comprises ananalog-to-digital converter (ADC) that includes an amplifier having aninput and an output; N capacitances that are connected in parallel andthat include first ends that selectively communicate with the input andsecond ends; N switches that selectively connect the second ends of theN capacitances to the voltage input during a first phase, one of thesecond ends of the N capacitances to the output of the amplifier duringa second phase, and others of the second ends of the N capacitances toone of a voltage reference and a reference potential during the secondphase. A second stage communicates with the output the amplifier.

In other features, the first phase is a sampling phase and the secondphase is a residue amplification phase. When the input voltage isbetween zero and a first ratio of a first of the N capacitances dividedby a sum of the N capacitances, the first of the N capacitances isconnected to the output of the amplifier and others of the Ncapacitances are connected to the reference potential during the secondphase. When the input voltage is between the first ratio and a secondratio of a sum of the first and a second of the N capacitances dividedby a sum of the N capacitances, the first of the N capacitances isconnected to the voltage reference, the second of the N capacitances isconnected to the output of the amplifier and others of the Ncapacitances are connected to the reference potential during the secondphase. When the input voltage is between the second ratio and a thirdratio of a sum of the first, the second and a third of the Ncapacitances divided by a sum of the N capacitances, the first and thesecond of the N capacitances are connected to the voltage reference, thethird of the N capacitances is connected to the output of the amplifierand others of the N capacitances are connected to the referencepotential during the second phase.

A pipelined analog-to-digital converter (ADC) comprises first stagemeans for receiving an input voltage signal and that comprisesconverting means for converting signals that includes: amplifying meansfor amplifying and having an input and an output; N capacitance meansfor providing capacitance, that are connected in parallel and thatinclude first ends that selectively communicate with the input andsecond ends; and N switching means for selectively connecting the secondends of the N capacitance means to the voltage input during a firstphase, one of the second ends of the N capacitance means to the outputof the amplifier during a second phase, and others of the second ends ofthe N capacitance means to one of a voltage reference and a referencepotential during the second phase; and second stage means forcommunicating with the output of the amplifying means of the first stagemeans.

In other features, the first phase is a sampling phase and the secondphase is a residue amplification phase. When the input voltage isbetween zero and a first ratio of a first of the N capacitances dividedby a sum of the N capacitances, the N switching means connect the firstof the N capacitances to the output of the amplifier and others of the Ncapacitances to the reference potential during the second phase. Whenthe input voltage is between the first ratio and a second ratio of a sumof the first and a second of the N capacitances divided by a sum of theN capacitances, the N switching means connect the first of the Ncapacitances to the voltage reference, the second of the N capacitancesto the output of the amplifier and others of the N capacitances to thereference potential during the second phase. When the input voltage isbetween the second ratio and a third ratio of a sum of the first, thesecond and a third of the N capacitances divided by a sum of the Ncapacitances, the N switching means connect the first and the second ofthe N capacitances to the voltage reference, the third of the Ncapacitances to the output of the amplifier and others of the Ncapacitances to the reference potential during the second phase.

A method for generating a residue voltage in a pipelinedanalog-to-digital converter (ADC) comprises providing first and secondstages, wherein the first stage receives a voltage input and includes acapacitive ADC including N capacitances; selectively connecting thesecond ends of the N capacitances to the voltage input during a firstphase; selectively connecting one of the second ends of the Ncapacitances to the output of the amplifier during a second phase;selectively connecting others of the second ends of the N capacitancesto one of a voltage reference and a reference potential during thesecond phase; selectively connecting the first ends of the Ncapacitances to an amplifier input; and connecting an amplifier outputto the second stage.

In other features, the first phase is a sampling phase and the secondphase is a residue amplification phase. The method further comprisesselectively connecting the first of the N capacitances to the output ofthe amplifier and others of the N capacitances to the referencepotential during the second phase when the input voltage is between zeroand a first ratio of a first of the N capacitances divided by a sum ofthe N capacitances. The method further comprises selectively connectingthe first of the N capacitances to the voltage reference, the second ofthe N capacitances to the output of the amplifier and others of the Ncapacitances to the reference potential during the second phase when theinput voltage is between the first ratio and a second ratio of a sum ofthe first and a second of the N capacitances divided by a sum of the Ncapacitances. The method further comprises selectively connecting thefirst and the second of the N capacitances to the voltage reference, thethird of the N capacitances to the output of the amplifier and others ofthe N capacitances to the reference potential during the second phasewhen the input voltage is between the second ratio and a third ratio ofa sum of the first, the second and a third of the N capacitances dividedby a sum of the N capacitances.

A digital to analog converter (DAC) comprises X capacitive DACs that areconnected in series and wherein X is an integer greater than one. Eachof the X capacitive DACs comprise M switches wherein M is an integergreater than one; a signal input; a signal output; and M capacitancesthat communicate with the M switches, respectively, and that have firstand second ends and substantially equal capacitance values. The Mswitches selectively connect the first ends of the M capacitances to thesignal output. The M switches connect the second end of a selected oneof the M capacitances to the signal input. A first DAC has a signaloutput that communicates with the signal input of one of the Xcapacitive DACs.

In other features, an amplifier has an input and an output. A feedbackcapacitance communicates with the input and the output of the amplifier.The first ends of the M capacitances of another one of the X DACscommunicates with a reference potential during a first phase of theanother one of the X DACs. The input of the amplifier selectivelycommunicates with the first ends of the M capacitances of the anotherone of the X DACs during a second phase of the another one of the XDACs.

In other features, an amplifier has an input and an output. The firstends of the M capacitances of another one of the X DACs communicate witha reference potential during a first phase of the another one of the XDACs. The input of the amplifier selectively communicates with the firstends of the M capacitances of the another one of the X DACs during asecond phase of the another one of the X DACs. The second ends of the ofthe M capacitances of the another one of the X DACs communicate with theoutput of the amplifier during the second phase of the another one ofthe X DACs. The first DAC comprises Y resistive DACs wherein Y is aninteger greater than zero.

In other features, at least one of the Y resistive DACs comprises asignal output; N resistances connected in series between the voltagereference and the reference potential; N nodes between select ones ofthe N resistances and the reference potential; and N second switchesthat selectively connect the signal output of the one of the Y resistiveDACs to one of the N nodes. A control module selectively generatesswitching signals to control the X capacitive DACs and the first DAC.

In other features, a successive approximation analog-to-digitalconverter comprises the DAC. The successive approximationanalog-to-digital converter of comprises an amplifier having an inputthat selectively communicates with one of the X capacitive DACs. Asuccessive approximation module communicates with an output of theamplifier. A decoding module communicates with an output of thesuccessive approximation module and selectively generates switchingsignals for the X capacitive DACs and the first DAC.

In other features, the first DAC comprises a capacitive DAC. Thecapacitive DAC comprises a signal output and an amplifier having aninput and an output that communicates with the signal output. M secondcapacitances are connected in parallel and have first ends and secondends. The first ends selectively communicate with a reference potentialduring a first phase of the capacitive DAC. The first ends selectivelycommunicate with the input of the amplifier during a second phase of thecapacitive DAC. M second switches selectively connect the second ends ofthe M second capacitances to one of the voltage reference and thereference potential during the first phase of the capacitive DAC andselectively connect the second ends of the M second capacitances to theoutput during the second phase of the capacitive DAC.

A digital to analog converter (DAC) comprises X capacitive convertingmeans for converting a digital signal to an analog signal and that areconnected together in series and wherein X is an integer greater thanone. Each of the X capacitive converting means comprise M switchingmeans for switching wherein M is an integer greater than one. Mcapacitance means for providing capacitance communicate with the Mswitching means, respectively, and have first and second ends andsubstantially equal capacitance values. The M switching meansselectively connect the first ends of the M capacitance means to thesignal output. The M switching means connect the second end of aselected one of the M capacitance means to the signal input. Firstconverting means converts a digital signal to an analog signal and has asignal output that communicates with the signal input of one of the Xcapacitive converting means.

In other features, amplifying means for amplifying and has an input andan output. Feedback capacitance means provides capacitance andcommunicates with the input and the output of the amplifying means. Thefirst ends of the M capacitance means of another one of the X convertingmeans communicates with a reference potential during a first phase ofthe another one of the X converting means. The input of the amplifyingmeans selectively communicates with the first ends of the M capacitancemeans of the another one of the X converting means during a second phaseof the another one of the X converting means.

In other features, amplifying means for amplifying has an input and anoutput. The first ends of the M capacitance means of another one of theX converting means communicates with a reference potential during afirst phase of the another one of the X converting means. The input ofthe amplifying means selectively communicates with the first ends of theM capacitance means of the another one of the X converting means duringa second phase of the another one of the X converting means. The secondends of the M capacitance means of the another one of the X convertingmeans communicate with the output of the amplifying means during thesecond phase of the another one of the X converting means. The first DACcomprises Y resistive converting means for converting a digital signalto an analog signal and wherein Y is an integer greater than zero.

In other features, at least one of the Y resistive converting meanscomprises a signal output and N resistance means for providingresistance and that is connected in series between the voltage referenceand the reference potential. N nodes are located between select ones ofthe N resistance means and the reference potential. N second switchingmeans selectively connect the signal output of the one of the Yresistive converting means to one of the N nodes. Control meansselectively generates switching signals to control the X capacitiveconverting means and the first DAC.

In other features, a successive approximation analog-to-digitalconverter comprises the DAC. The successive approximationanalog-to-digital converter comprises amplifying means for amplifyingand having an input that selectively communicates with one of the Xcapacitive DACs and approximation means for successive approximating andthat communicates with an output of the amplifying means. Decoding meanscommunicates with an output of the successive approximation module forselectively generating switching signals for the X capacitive DACs andthe first DAC.

In other features, the first DAC comprises a capacitive converting meansfor converting a digital signal to an analog signal. The capacitiveconverting means comprises a signal output and amplifying means foramplifying and having an input and an output that communicates with thesignal output. M second capacitance means provides capacitance and isconnected in parallel and has first ends and second ends. The first endsselectively communicate with a reference potential during a first phaseof the capacitive DAC. The first ends selectively communicate with theinput of the amplifying means during a second phase of the capacitiveDAC. M second switching means selectively connect the second ends of theM second capacitance means to one of the voltage reference and thereference potential during the first phase of the capacitive DAC andselectively connect the second ends of the M second capacitance means tothe output during the second phase of the capacitive DAC.

A method for operating a digital to analog converter (DAC) comprisesconnecting X capacitive DACs in series and wherein X is an integergreater than one, wherein each of the X capacitive DACs comprise Mcapacitances that have first and second ends and substantially equalcapacitance values; selectively connecting the first ends of the Mcapacitances to the signal output; connecting the second end of aselected one of the M capacitances to the signal input; and connecting asignal output of a first DAC to the signal input of one of the Xcapacitive DACs.

In other features, the method comprises providing an amplifier having aninput and an output and a feedback capacitance that communicates withthe input and the output of the amplifier. The method comprisesconnecting the first ends of the M capacitances of another one of the XDACs with a reference potential during a first phase of the another oneof the X DACs. The method comprises selectively connecting the input ofthe amplifier to the first ends of the M capacitances of the another oneof the X DACs during a second phase of the another one of the X DACs.

In other features, the method comprises providing an amplifier having aninput and an output; selectively connecting the first ends of the Mcapacitances of another one of the X DACs with a reference potentialduring a first phase of the another one of the X DACs; selectivelyconnecting the input of the amplifier with the first ends of the Mcapacitances of the another one of the X DACs during a second phase ofthe another one of the X DACs; and selectively connecting the secondends of the of the M capacitances of the another one of the X DACscommunicate with the output of the amplifier during the second phase ofthe another one of the X DACs.

In other features, the first DAC comprises Y resistive DACs wherein Y isan integer greater than zero. The method comprises selectivelygenerating switching signals to control the X capacitive DACs and thefirst DAC. The method comprises using the X capacitive DACs tosuccessively approximate an analog input signal. The first DAC comprisesa capacitive DAC.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1A is an electrical schematic of a binary capacitor array D/Aconverter according to the prior art;

FIG. 1B is a graph of a D/A converter;

FIG. 2 is an electrical schematic of a linear capacitor array D/Aconverter according to a prior art;

FIGS. 3A-3C are electrical schematics of a capacitive-resistive D/Aconverter in exemplary configurations;

FIG. 4A illustrates the D/A converter of FIG. 3B during a sampling phasefor a first digital value;

FIG. 4B illustrates the D/A converter of FIG. 3B during an integratingphase for a first digital value;

FIG. 4C is an exemplary truth table for the circuit of FIG. 3B;

FIG. 4D is an exemplary truth table for the circuit of FIG. 3C;

FIG. 5 illustrates the D/A converter of FIG. 3B during a sampling phasefor a second digital value;

FIG. 6 illustrates the D/A converter of FIG. 3B during a sampling phasefor a third digital value;

FIG. 7 illustrates the D/A converter of FIG. 3B during a sampling phasefor a fourth digital value;

FIG. 8A is an electrical schematic of a capacitive-capacitive D/Aconverter;

FIG. 8B is an electrical schematic of a capacitive-capacitive D/Aconverter in a sample and integrate configuration;

FIG. 8C illustrates the D/A converter of FIG. 8B during a sampling phasefor a first digital value;

FIG. 8D illustrates the D/A converter of FIG. 8B during an integratingphase for a first digital value;

FIG. 8E illustrates the D/A converter of FIG. 8B during a sampling phasefor a second digital value;

FIG. 8F illustrates the D/A converter of FIG. 8B during a sampling phasefor a third digital value;

FIG. 8G illustrates the D/A converter of FIG. 8B during a sampling phasefor a fourth digital value;

FIG. 8H is an exemplary timing diagram showing sampling and integratingphases for LSB and MSB portions;

FIG. 8I is an exemplary timing diagram showing sampling and integratingphases for LSB and MSB portions;

FIG. 8J is an exemplary truth table for the D/A converter of FIG. 8B;

FIG. 9A illustrates an N-stage capacitive D/A converter;

FIG. 9B illustrates an N-stage capacitive-resistive D/A converter;

FIG. 9C is an exemplary timing diagram showing non-overlapping samplingand integrating phases for additional stages;

FIG. 9D is an exemplary timing diagram showing overlapping sampling andintegrating phases for additional stages;

FIG. 10 is an electrical schematic of a successive approximation A/Dconverter according to the present invention;

FIG. 11A is an electrical schematic of a pipelined A/D converteraccording to the present invention;

FIGS. 11B-11D illustrate ideal and non-ideal residue voltages;

FIG. 12A illustrates an A/D converter that generates an ideal residuevoltage according to the present invention;

FIG. 12B illustrates the A/D converter of FIG. 12A in a sampling phase;

FIG. 12C illustrates the A/D converter of FIG. 12A in a residueamplification stage for a first voltage input value;

FIG. 12D is an exemplary truth table for the A/D converter of FIG. 12A;

FIG. 13 illustrates the A/D converter of FIG. 12A in a residueamplification stage for a second voltage input value;

FIG. 14 illustrates the A/D converter of FIG. 12A in a residueamplification stage for a third voltage input value;

FIG. 15 illustrates the A/D converter of FIG. 12A in a residueamplification stage for a fourth voltage input value;

FIG. 16 is a graph illustrating variable interstage gain and an idealresidue voltage of the circuit of FIG. 12A;

FIG. 17A is a functional block diagram of a hard disk drive;

FIG. 17B is a functional block diagram of a digital versatile disk(DVD);

FIG. 17C is a functional block diagram of a high definition television;

FIG. 17D is a functional block diagram of a vehicle control system;

FIG. 17E is a functional block diagram of a cellular phone;

FIG. 17F is a functional block diagram of a set top box; and

FIG. 17G is a functional block diagram of a media player.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. For purposes of clarity, the same referencenumbers will be used in the drawings to identify similar elements. Asused herein, the term module, circuit and/or device refers to anApplication Specific Integrated Circuit (ASIC), an electronic circuit, aprocessor (shared, dedicated, or group) and memory that execute one ormore software or firmware programs, a combinational logic circuit,and/or other suitable components that provide the describedfunctionality. As used herein, the phrase at least one of A, B, and Cshould be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present invention.

Referring now to FIGS. 3A and 3B, capacitive-resistive D/A converters100, 100-1 and 100-2 are shown. For simplicity, an N=4 bit example isshown in FIGS. 3A-3C. Skilled artisans will appreciate that N can be setto other numbers of bits. Various types of output circuits 102 may beused. Additional connections 104, which may or may not be switchedconnections, may be used depending upon the function that is desired.For example in FIG. 3B, the DAC 100-1 is shown in a sample and integrateconfiguration and in FIG. 3C, a DAC 100-2 is shown with a sample andhold configuration.

In this example, the two most significant bits (MSBs) are allocated to acapacitive portion 110 and the two least significant bits (LSBs) areallocated to a resistive portion 120. In the Figures that follow, thecapacitor C_(f) will be shown with dotted lines to indicate both sampleand hold and sample and integrate configurations.

The capacitive portion 110 includes capacitors C₁, C₂, C₃ and C₄. In thepreferred embodiment, the capacitors C₁, C₂, C₃ and C₄ have asubstantially equal capacitance value. The capacitors may havesubstantially the same capacitance value, in other words C₁=C₂=C₃=C₄. Aswill be described further below, the capacitors are selectively switchedby switches SW_(4MSB), SW_(3MSB), SW_(2MSB), and SW_(1MSB) (collectivelyswitches SW_(M)) between a voltage reference V_(ref), a referencepotential such as ground, and a common node 130 between the resistiveportion 120 and the capacitive portion 110.

The resistive portion 110 includes resistors R₁, R₂, R₃ and R₄. In thepreferred embodiment, the resistors R₁, R₂, R₃ and R₄ have asubstantially equal resistance value. The resistors may have the sameresistance value, in other words R₁=R₂=R₃=R₄. As will be describedfurther below, the resistors are connected in series between V_(ref) anda reference potential such as ground. A node between the resistors isselected by switches SW_(4LSB), SW_(3LSB), SW_(2LSB), and SW_(1LSB)(collectively switches SW_(L)) and connected to the common node 130 tocreate a voltage divider.

The sample and integrate circuit was described above. In the sample andhold configuration, the second ends of the capacitances C₁, C₂, C₃ andC₄ are switched to the output of the amplifier during the second phaseof the capacitive portion 110. The feedback capacitance C_(f) may beomitted.

Referring now to FIG. 4A, the D/A converter of FIG. 3B is shown during asampling phase for a first digital value (0011). Initially, the switch16 is closed, the switch 18 is opened and the capacitors C₂, C₃ and C₄are switched by respective switches to the reference potential, whichmay be ground. The capacitor C₁ is connected to the common node. Thecapacitive portion 110 will be in this configuration when the desiredbinary value is between 0000 and 0011. One of the resistive switchesSW_(4LSB), SW_(3LSB), SW_(2LSB), and SW_(1LSB) is closed to create avoltage divider. In the example shown in FIG. 4A, the switch SW_(4LSB)is closed to provide $\frac{3}{4}{V_{ref}.}$A charge is accumulated on the capacitor C₁ that is equal to V_(RDAC)C₁,where V_(RDAC) is the voltage provided by the resistive portion 120.

Referring now to FIG. 4B, the D/A converter of FIG. 3B is shown duringan integrating phase for the first digital value (0011). In this phase,the switch 16 is opened, the switch 18 is closed and the voltage valueis applied to the amplifier 20. Using a charge equalization approach,the total charge before changing the position of the switches 16 and 18is equal to the total charge after changing the position of the switches16 and 18: Q_(T) = VC_(f) = V_(RDAC)C₁;$V = {V_{RDAC}{\frac{C_{1}}{C_{f}}.}}$The value of C_(f) can be set equal to C₁, C₂, C₃ and C₄ or be used toscale the output voltage and not be equal to C₁, C₂, C₃ and C₄. In theexample above, $V_{RDAC} = {\frac{3}{4}{V_{ref}.}}$As can be appreciated, the value can also be adjusted to${V_{RDAC} = 0},{V_{RDAC} = {\frac{1}{4}V_{ref}}},{{{or}\quad V_{RDAC}} = {\frac{1}{2}V_{ref}}}$by selecting the switch SW_(1LSB), SW_(2LSB) or SW_(3LSB), respectively.Scaling can be performed by adjusting the value of C_(f) relative to C₁,C₂, C₃ and C₄. For example, if C_(f)=C₁+C₂+C₃+C₄, then the output ranges0 to near V_(ref) rather than 0 to near 4 V_(ref) in this example.

Referring now to FIG. 4C, a truth table for the exemplary converter ofFIG. 3B is shown. In this example, C_(f) is equal to C₁, C₂, C₃ and C₄although other values may be used for scaling. Referring now to FIG. 4D,a truth table for the exemplary converter of FIG. 3C is shown.

Referring now to FIG. 5, the D/A converter of FIG. 3B is shown during anintegrating phase for a second digital value (0111). Initially, theswitch 16 is closed, the switch 18 is opened and the capacitors C₃ andC₄ are switched by respective switches to the reference potential, whichmay be ground. The capacitor C₂ is connected to the common node 130 andthe capacitor C₁ is connected to V_(ref). The capacitive portion 110will be in this configuration when the desired binary value is between0100 and 0111. One of the resistive switches SW_(4LSB), SW_(3LSB),SW_(2LSB), and SW_(1LSB) is closed to create a voltage divider. In theexample shown in FIG. 5, the switch SW_(4LSB) is closed to provide$\frac{3}{4}{V_{ref}.}$A charge is accumulated on the capacitor C₂ that is equal to V_(RDAC)C₂,where V_(RDAC) is the voltage provided by the resistive portion. Acharge is also accumulated on capacitor C₁ equal to V_(ref)C₁.

During an integrating phase for the second digital value (0111). theswitch 16 is opened, the switch 18 is closed and the voltage value isapplied to the amplifier 20. Using a charge equalization approach, thetotal charge before changing the position of the switches 16 and 18 isequal to the total charge after changing the position of the switches 16and 18: Q_(T) = VC_(f) = V_(RDAC)C₂ + V_(ref)C₁;$V = {{V_{RDAC}\frac{C_{2}}{C_{f}}} + {V_{ref}{\frac{C_{1}}{C_{f}}.}}}$The value of C_(f) can be set equal to C₁, C₂, C₃ and C₄ or be used toscale the output voltage and not be equal to C₁, C₂, C₃ and C₄. IfC_(f), C₁ and C₂ are the same, V=V_(RDAC)+V_(ref).

Referring now to FIG. 6, the D/A converter of FIG. 3B is shown during anintegrating phase for a third digital value (1011). Initially, theswitch 16 is closed, the switch 18 is opened and the capacitor C₄ isswitched by a respective switch to the reference potential, which may beground. The capacitor C₃ is connected to the common node 130 and thecapacitors C₁ and C₂ are connected to V_(ref). The capacitive portion110 will be in this configuration when the desired binary value isbetween 1000 and 1011. One of the resistive switches SW_(4LSB),SW_(3LSB), SW_(2LSB), and SW_(1LSB) is closed to create a voltagedivider. In the example shown in FIG. 6, the switch SW_(4LSB) is closedto provide $\frac{3}{4}{V_{ref}.}$A charge is accumulated on the capacitor C₃ that is equal to V_(RDAC)C₃,where V_(RDAC) is the voltage provided by the resistive portion. Acharge is also accumulated on capacitors C₁ and C₂ that is equal toV_(ref)(C₁+C₂).

During an integrating phase for the third digital value (1011). theswitch 16 is opened, the switch 18 is closed and the voltage value isapplied to the amplifier 20. Using a charge equalization approach, thetotal charge before changing the position of the switches 16 and 18 isequal to the total charge after changing the position of the switches 16and 18: Q_(T) = VC_(f) = V_(RDAC)C₃ + V_(ref)(C₁ + C₂);$V = {{V_{RDAC}\frac{C_{3}}{C_{f}}} + {V_{ref}{\frac{C_{1} + C_{2}}{C_{f}}.}}}$The value of C_(f) can be set equal to C₁, C₂, C₃ and C₄ or be used toscale the output voltage and not be equal to C₁, C₂, C₃ and C₄. IfC_(f), C₁, C₂ and C₃ are the same, V=V_(RDAC)+2V_(ref).

Referring now to FIG. 7, the D/A converter of FIG. 3B is shown during anintegrating phase for a third digital value (1111). Initially, theswitch 16 is closed and the switch 18 is opened. The capacitor C₄ isconnected to the common node 130 and the capacitors C₁, C₂ and C₃ areconnected to V_(ref). The capacitive portion 110 will be in thisconfiguration when the desired binary value is between 1100 and 1111.One of the resistive switches SW_(4LSB), SW_(3LSB), SW_(2LSB), andSW_(1LSB) is closed to create a voltage divider. In the example shown inFIG. 7, the switch SW_(4LSB) is closed to provide$\frac{3}{4}{V_{ref}.}$A charge is accumulated on the capacitor C₄ that is equal to V_(RDAC)C₄,where V_(RDAC) is the voltage provided by the resistive portion. Acharge is accumulated on capacitors C₁, C₂ and C₃ that is equal toV_(ref)(C₁+C₂+C₃) .

During an integrating phase for the fourth digital value (1111). theswitch 16 is opened, the switch 18 is closed and the voltage value isapplied to the amplifier 20. Using a charge equalization approach, thetotal charge before changing the position of the switches 16 and 18 isequal to the total charge after changing the position of the switches 16and 18: Q_(T) = VC_(f) = V_(RDAC)C₄ + V_(ref)(C₁ + C₂ + C₃);$V = {{V_{RDAC}\frac{C_{4}}{C_{f}}} + {V_{ref}{\frac{C_{1} + C_{2} + C_{3}}{C_{f}}.}}}$The value of C_(f) can be set equal to C₁, C₂, C₃ and C₄ or be used toscale the output voltage and not be equal to C₁, C₂, C₃ and C₄. IfC_(f), C₁, C₂, C₃ and C₄ are the same, V=V_(RDAC)+3V_(ref).

Referring now to FIGS. 8A and 8B, a nested segmentedcapacitive-capacitive D/A converter 108 according to the presentinvention is shown. In FIG. 8A, the output circuit 102 is shown. In FIG.8B, an exemplary sample and integrate configuration is shown. Thecapacitive portion 110 operates as described above. For purposes ofclarity, the capacitors C₁, C₂, C₃ and C₄ have been relabeled C_(1M),C_(2M), C_(3M) and C_(4M). A second capacitive portion 150 is associatedwith the two least significant bits and includes capacitors C_(1L),C_(2L), C_(3L) and C_(4L). The voltage provided by the LSB capacitiveportion 150 is V_(CDAC). The second capacitive portion 150 also has asampling and integrating phase as will be described below.

Referring now to FIGS. 8C and 8D, an equivalent circuit of the D/Aconverter of FIG. 8B during a sampling phase is shown for$V_{CDAC} = {\frac{V_{ref}}{4}.}$During sampling phase, the switch 152 is closed and the capacitorsC_(4L), C_(3L) and C_(2L) are connected to a reference potential such asground. The capacitor C_(1L) is charged to V_(ref). A charge isaccumulated on the capacitor C_(1L) that is equal to V_(ref)C_(1L).

During the integrating phase, the switch 152 is opened and thecapacitors C_(4L), C_(3L), C_(2L) and C_(1L) are connected in feedback.The total charge before the switch 152 is opened is the same as thetotal charge after the switch 152 is opened. Therefore:Q_(T) = VC_(T) = V_(ref)C_(1L) = V(C_(1L) + C_(2L) + C_(3L) + C_(4L));$V = {V_{ref}{\frac{C_{1L}}{C_{1L} + C_{2L} + C_{32L} + C_{4L}}.}}$Assuming that C_(1L), C_(2L), C_(3L) and C_(4L) are equal,$V = {\frac{V_{ref}}{4}.}$

Referring now to FIG. 8E, an equivalent circuit of the D/A converter ofFIG. 8B during a sampling phase is shown for$V_{CDAC} = {\frac{V_{ref}}{2}.}$During sampling phase, the switch 152 is closed and the capacitorsC_(4L) and C_(3L) are connected to a reference potential such as ground.The capacitors C_(1L) and C_(2L) are charged to V_(ref). A charge isaccumulated on the capacitors C_(1L) and C_(2L) that is equal toV_(ref)(C_(1L)+C_(2L)).

During the integrating phase, the switch 152 is opened and thecapacitors C_(4L), C_(3L), C_(2L) and C_(1L) are connected in feedback.The total charge before the switch 152 is opened is the same as thetotal charge after the switch 152 is opened. Therefore:Q_(T) = VC_(T) = V_(ref)(C_(1L) + C_(2L)) = V(C_(1L) + C_(2L) + C_(3L) + C_(4L));$V = {V_{ref}{\frac{C_{1L} + C_{2L}}{( {C_{1L} + C_{2L} + C_{3L} + C_{4L}} )}.}}$Assuming that C₁, C₂, C₃ and C₄ are equal, $V = {\frac{V_{ref}}{2}.}$

Referring now to FIG. 8F, an equivalent circuit of the D/A converter ofFIG. 8B during a sampling phase is shown for$V_{CDAC} = {\frac{3V_{ref}}{4}.}$During sampling phase, the switch 152 is closed and the capacitor C_(4L)is connected to a reference potential such as ground. The capacitorsC_(1L), C_(2L) and C_(3L) are charged to V_(ref). A charge isaccumulated on the capacitors C_(1L), C_(2L) and C_(3L) that is equal toV_(ref)(C_(1L)+C_(2L)+C_(3L)).

During the integrating phase, the switch 152 is opened and thecapacitors C_(4L), C_(3L), C_(2L) and C_(1L) are connected in feedback.The total charge before the switch 152 is opened is the same as thetotal charge after the switch 152 is opened. Therefore:Q_(T) = VC_(T) = V_(ref)(C_(1L) + C_(2L) + C_(3L)) = V(C_(1L) + C_(2L) + C_(3L) + C_(4L));$V = {V_{ref}{\frac{C_{1L} + C_{2L} + C_{3L}}{( {C_{1L} + C_{2L} + C_{3L} + C_{4L}} )}.}}$Assuming that C_(1L), C_(2L), C_(3L) and C_(4L) are equal,$V = {\frac{3V_{ref}}{4}.}$

Referring now to FIG. 8G, an equivalent circuit of the D/A converter ofFIG. 8B during a sampling phase is shown for V_(CDAC)=V_(ref). Theswitch associated with this position may be omitted since this value canbe already be obtained by using the next MSB. In this case one of thecapacitors may always be connected to ground. If a switch is used,during sampling phase the switch 152 is closed and the capacitorsC_(1L), C_(2L), C_(3L) and C_(4L) are charged to V_(ref). A charge isaccumulated on the capacitors C_(1L), C_(2L), C_(3L) and C_(4L) that isequal to V_(ref)(C_(1L)+C_(2L)+C_(3L)+C_(4L)).

During the integrating phase, the switch 152 is opened and thecapacitors C_(4L), C_(3L), C_(2L) and C_(1L) are connected in feedback.The total charge before the switch 152 is opened is the same as thetotal charge after the switch 152 is opened. Therefore:Q_(T) = VC_(T) = V_(ref)(C_(1L) + C_(2L) + C_(3L) + C_(4L)) = V(C_(1L) + C_(2L) + C_(3L) + C_(4L));$V = {V_{ref}{\frac{C_{1L} + C_{2L} + C_{3L} + C_{4L}}{( {C_{1L} + C_{2L} + C_{3L} + C_{4L}} )}.}}$

Assuming that C_(1L), C_(2L), C_(3L) and C_(4L) are equal, V=V_(ref).

Referring now to FIGS. 8H and 8I, non-overlapping and overlapping timingdiagrams are shown for sampling and integrating phases for LSB and MSBcapacitive portions. The timing of the sampling and integrating phasescan be non-overlapping as shown in FIG. 8H. Alternately, the samplingphase of the LSB capacitive portion can fully and/or partially overlapthe integrating phase of the MSB capacitive portion as shown in FIG. 8I.

Referring now to FIG. 8J, a truth table for the D/A converter is shown.As can be appreciated, the LSB switches can be connected in feedbackand/or to ground during the MSB-integrating phase and/or can begin thenext LSB sampling phase as described herein.

Referring now to FIGS. 9A-9D, additional capacitive and/or resistive DACportions may be added. In FIG. 9A, an N stage capacitive D/A converter170 is shown. The converter 170 includes capacitive portions BG₁, BG₂, .. . , and BG_(X), which are associated with LSB, next LSB, . . . , andMSB groups. For example, a 6 bit example can include capacitive portionsBG₁, BG₂ and BG₃. Each capacitive portion may include four capacitors asshown and described above. Each of the capacitive portions includessampling and integrating stages that may be non-overlapping and/oroverlapping as described above and below.

In FIG. 9B, an N stage capacitive-resistive D/A converter 180 is shown.One or more of the last stages is a resistive portion as describedabove. In this example, there are X-Y capacitive portions and Yresistive portions, where X and Y are integers greater than zero. Whenresistive portions are used, the sampling and integrating phases for thelast capacitive stage and the final resistive stage can be the same asdescribed above. In FIG. 9C, an exemplary timing diagram showsnon-overlapping sampling and integrating phases for additionalcapacitive stages. In FIG. 9D, an exemplary timing diagram showing fullyand/or partially overlapping sampling and integrating phases foradditional capacitive stages is shown.

Referring now to FIG. 10, a successive approximation A/D converter 200is shown. The converter 200 includes a successive approximation register(SAR) 204 or module that contains logic for resolving the digital bitsas will be described further below. An output of the SAR 204 is input todecoder module 209 that may include a modified thermometer decoder 210that communicates with and controls switches SW_(4MSB), SW_(3MSB),SW_(2MSB), and SW_(1MSB) based on MSBs of the output of the SAR. Anoutput of the SAR 204 is input to a thermometer decoder 220 thatcommunicates with and controls switches SW_(4LSB), SW_(3LSB), SW_(2LSB),and SW_(1LSB) based on LSBs in the output of the SAR 204.

During acquisition, the switch 16 is connected to ground. Ends of thecapacitors are connected by switches SW_(MSB) to V_(in). Afteracquisition of V_(in), the switch 16 is opened and the capacitors aredisconnected by switches SW_(MSB) from V_(in). The capacitor array ischarged with a voltage based on V_(in). The capacitors are thenconnected to ground by switches SW_(MSB), which drives the commonterminal negative to a voltage equal to −V_(in).

As the first step in a binary search algorithm, the capacitive andresistive portions are configured to provide ½V_(ref) as describedabove. In other words, C_(4M) is connected to the common node, C_(3M),C_(2M) and C_(1M) are connected to V_(ref) and the switch SW_(1LSB) isclosed. For example, if V_(in) is equal to ¾V_(ref), the common terminalwill be driven to (−¾V_(ref)+½V_(ref))=−¼V_(ref). When this voltage iscompared to ground, the output of the comparator 20 yields a logic ‘1’,implying that V_(in) is greater than ½V_(ref). If V_(in) is equal to¼V_(ref), the common terminal voltage is (−¼V_(ref)+½V_(ref))=+¼V_(ref),and the output of the comparator 20 is a logic ‘0’. This processcontinues with the next MSB or LSB depending upon the value of thecomparator output until all bits are resolved. Whilecapacitive-resistive implementation is shown, capacitive-capacitive,N-stage capacitive or N-stage capacitive-resistive implementations arealso contemplated.

Referring now to FIG. 11A, a pipelined A/D converter 250 is shown. Theconverter 250 includes a plurality of stages 252-1, 252-2, 252-3(collectively 252) that are cascaded in series. Each of the course A/Dconverter stages 252 includes a sample and hold module 254 that samplesand holds the analog output signal from a prior stage, a low resolutionA/D subconverter module 256 that converts the held analog signal, alow-resolution D/A subconverter module 258 that converts the resultingdigital output back into an analog representation, a difference module260 and an analog interstage difference amplifier module 262 thatamplifies the residue. The residue is the difference between the heldanalog signal and the reconstructed analog signal.

The first stage 252-1 of the pipelined A/D converter 250 operates on amost current analog input sample while the second stage 252-2 operateson the amplified residue of the previous input sample. The concurrencyof operations results in a conversion speed that is determined only bythe time it takes in one stage.

Referring now to FIGS. 11B-11D, ideal and non-ideal residue voltages areshown. In FIG. 11B, an ideal residue voltage is shown. When the inputreaches a first decision level of the A/D subconverter module 252, theoutput of the subconverter module switches to its next higher level codecausing the output of the D/A subconverter to switch to its next higherlevel. This in turn causes the amplified residue to drop back to zero.

In actual implementations, however, the components are not ideal andnon-uniformity occurs. In FIG. 11C, the residue voltage exceeds theideal value by a fixed amount. In FIG. 11D, the residue voltage exceedsthe ideal residue voltage by a variable amount.

Referring now to FIG. 12A, an analog to digital converter 300 thatgenerates a residue voltage with lower variation according to thepresent invention is shown. Capacitors C₁, C₂, C₃ and C₄ are selectivelyconnected to V_(in), a reference potential such as ground, a voltagereference (V_(ref)) and to an output of the opamp 20. In someimplementations, C₁, C₂, C₃ and C₄ have substantially equal capacitancevalues.

Referring now to FIGS. 12B-12D, the analog to digital converter of FIG.12A is shown further. In a sampling phase in FIG. 12B, the switch 16 isclosed and the capacitors are connected to V_(in). In a residueamplification stage in FIG. 12B for V_(in) between 0 and$\frac{C_{1}}{C_{1} + C_{2} + C_{3} + C_{4}}V_{ref}$(“A” in FIG. 12D), the switch 16 is opened, the capacitor C₁ isconnected in feedback arrangement. The capacitors C₂, C₃, and C₄ areconnected to the reference potential. A truth table is shown in FIG.12D.

Referring now to FIG. 13, in a residue amplification stage for V_(in)between$\frac{C_{1}}{C_{1} + C_{2} + C_{3} + C_{4}}V_{ref}\quad{and}\quad\frac{C_{1} + C_{2}}{C_{1} + C_{2} + C_{3} + C_{4}}V_{ref}$(“B” in FIG. 12D), the switch 16 is opened, the capacitor C₂ isconnected in feedback arrangement and the capacitor C₁ is connected toV_(ref). The capacitors C₃ and C₄ are connected to a referencepotential.

Referring now to FIG. 14, in a residue amplification stage for V_(in)between$\frac{C_{1} + C_{2}}{C_{1} + C_{2} + C_{3} + C_{4}}V_{ref}\quad{and}\quad\frac{C_{1} + C_{2} + C_{3}}{C_{1} + C_{2} + C_{3} + C_{4}}V_{ref}$(“C” in FIG. 12D), the switch 16 is opened, the capacitor C₃ isconnected in feedback arrangement and the capacitors C₁ and C₂ areconnected to V_(ref). The capacitor C₄ is connected to a referencepotential.

Referring now to FIGS. 15 and 16, in a residue amplification stage forV_(in) between$\frac{C_{1} + C_{2} + C_{3}}{C_{1} + C_{2} + C_{3} + C_{4}}V_{ref}$and V_(ref) (“D” in FIG. 12D), the switch 16 is opened, the capacitor C₄is connected in feedback arrangement and the capacitors C₁, C₂ and C₃are connected to V_(ref). Note that because the different capacitors areused as the feedback capacitor during residue amplification, the residuegain can perfectly track the capacitor mismatch. The residue voltage nowlooks as shown in FIG. 16. There is a variable inter-stage gain and asubstantially constant maximum residue voltage.

Referring now to FIGS. 17A-17G, various exemplary implementations of thepresent invention are shown. Referring now to FIG. 17A, the presentinvention can be implemented in D/A or A/D converters in a hard diskdrive 400. In some implementations, the signal processing and/or controlcircuit 402 and/or other circuits (not shown) in the HDD 400 may processdata, perform coding and/or encryption, perform calculations, and/orformat data that is output to and/or received from a magnetic storagemedium 406.

The HDD 400 may communicate with a host device (not shown) such as acomputer, mobile computing devices such as personal digital assistants,cellular phones, media or MP3 players and the like, and/or other devicesvia one or more wired or wireless communication links 408. The HDD 400may be connected to memory 409 such as random access memory (RAM), lowlatency nonvolatile memory such as flash memory, read only memory (ROM)and/or other suitable electronic data storage.

Referring now to FIG. 17B, the present invention can be implemented inD/A or A/D converters in a digital versatile disc (DVD) drive 410. Thesignal processing and/or control circuit 412 and/or other circuits (notshown) in the DVD 410 may process data, perform coding and/orencryption, perform calculations, and/or format data that is read fromand/or data written to an optical storage medium 416. In someimplementations, the signal processing and/or control circuit 412 and/orother circuits (not shown) in the DVD 410 can also perform otherfunctions such as encoding and/or decoding and/or any other signalprocessing functions associated with a DVD drive.

The DVD drive 410 may communicate with an output device (not shown) suchas a computer, television or other device via one or more wired orwireless communication links 417. The DVD 410 may communicate with massdata storage 418 that stores data in a nonvolatile manner. The mass datastorage 418 may include a hard disk drive (HDD). The HDD may have theconfiguration shown in FIG. 17A. The HDD may be a mini HDD that includesone or more platters having a diameter that is smaller thanapproximately 1.8″. The DVD 410 may be connected to memory 419 such asRAM, ROM, low latency nonvolatile memory such as flash memory and/orother suitable electronic data storage.

Referring now to FIG. 17C, the present invention can be implemented inD/A or A/D converters in a high definition television (HDTV) 420. TheHDTV 420 receives HDTV input signals in either a wired or wirelessformat and generates HDTV output signals for a display 426. In someimplementations, signal processing circuit and/or control circuit 422and/or other circuits (not shown) of the HDTV 420 may process data,perform coding and/or encryption, perform calculations, format dataand/or perform any other type of HDTV processing that may be required.

The HDTV 420 may communicate with mass data storage 427 that stores datain a nonvolatile manner such as optical and/or magnetic storage devices.At least one HDD may have the configuration shown in FIG. 17A and/or atleast one DVD may have the configuration shown in FIG. 17B. The HDD maybe a mini HDD that includes one or more platters having a diameter thatis smaller than approximately 1.8″. The HDTV 420 may be connected tomemory 428 such as RAM, ROM, low latency nonvolatile memory such asflash memory and/or other suitable electronic data storage. The HDTV 420also may support connections with a WLAN via a WLAN network interface429.

Referring now to FIG. 17D, the present invention may implement and/or beimplemented in D/A or A/D converters in a control system of a vehicle430, a WLAN interface, mass data storage of the vehicle control systemand/or a power supply 433. In some implementations, the presentinvention implement a powertrain control system 432 that receives inputsfrom one or more sensors such as temperature sensors, pressure sensors,rotational sensors, airflow sensors and/or any other suitable sensorsand/or that generates one or more output control signals such as engineoperating parameters, transmission operating parameters, and/or othercontrol signals.

The present invention may also be implemented in other control systems440 of the vehicle 430. The control system 440 may likewise receivesignals from input sensors 442 and/or output control signals to one ormore output devices 444. In some implementations, the control system 440may be part of an anti-lock braking system (ABS), a navigation system, atelematics system, a vehicle telematics system, a lane departure system,an adaptive cruise control system, a vehicle entertainment system suchas a stereo, DVD, compact disc and the like. Still other implementationsare contemplated.

The powertrain control system 432 may communicate with mass data storage446 that stores data in a nonvolatile manner. The mass data storage 446may include optical and/or magnetic storage devices for example harddisk drives HDD and/or DVDs. At least one HDD may have the configurationshown in FIG. 17A and/or at least one DVD may have the configurationshown in FIG. 17B. The HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″. Thepowertrain control system 432 may be connected to memory 447 such asRAM, ROM, low latency nonvolatile memory such as flash memory and/orother suitable electronic data storage. The powertrain control system432 also may support connections with a WLAN via a WLAN networkinterface 448. The control system 440 may also include mass datastorage, memory and/or a WLAN interface (all not shown).

Referring now to FIG. 17E, the present invention can be implemented inD/A or A/D converters in a cellular phone 450 that may include acellular antenna 451. In some implementations, the cellular phone 450includes a microphone 456, an audio output 458 such as a speaker and/oraudio output jack, a display 460 and/or an input device 462 such as akeypad, pointing device, voice actuation and/or other input device. Thesignal processing and/or control circuits 452 and/or other circuits (notshown) in the cellular phone 450 may process data, perform coding and/orencryption, perform calculations, format data and/or perform othercellular phone functions.

The cellular phone 450 may communicate with mass data storage 464 thatstores data in a nonvolatile manner such as optical and/or magneticstorage devices for example hard disk drives HDD and/or DVDs. At leastone HDD may have the configuration shown in FIG. 17A and/or at least oneDVD may have the configuration shown in FIG. 17B. The HDD may be a miniHDD that includes one or more platters having a diameter that is smallerthan approximately 1.8″. The cellular phone 450 may be connected tomemory 466 such as RAM, ROM, low latency nonvolatile memory such asflash memory and/or other suitable electronic data storage. The cellularphone 450 also may support connections with a WLAN via a WLAN networkinterface 468.

Referring now to FIG. 17F, the present invention can be implemented inD/A or A/D converters in a set top box 480. The set top box 480 receivessignals from a source such as a broadband source and outputs standardand/or high definition audio/video signals suitable for a display 488such as a television and/or monitor and/or other video and/or audiooutput devices. The signal processing and/or control circuits 484 and/orother circuits (not shown) of the set top box 480 may process data,perform coding and/or encryption, perform calculations, format dataand/or perform any other set top box function.

The set top box 480 may communicate with mass data storage 490 thatstores data in a nonvolatile manner. The mass data storage 490 mayinclude optical and/or magnetic storage devices for example hard diskdrives HDD and/or DVDs. At least one HDD may have the configurationshown in FIG. 17A and/or at least one DVD may have the configurationshown in FIG. 17B. The HDD may be a mini HDD that includes one or moreplatters having a diameter that is smaller than approximately 1.8″. Theset top box 480 may be connected to memory 494 such as RAM, ROM, lowlatency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. The set top box 480 also may supportconnections with a WLAN via a WLAN network interface 496.

Referring now to FIG. 17G, the present invention can be implemented inD/A or A/D converters in a media player 500. In some implementations,the media player 500 includes a display 507 and/or a user input 508 suchas a keypad, touchpad and the like. In some implementations, the mediaplayer 500 may employ a graphical user interface (GUI) that typicallyemploys menus, drop down menus, icons and/or a point-and-click interfacevia the display 507 and/or user input 508. The media player 500 furtherincludes an audio output 509 such as a speaker and/or audio output jack.The signal processing and/or control circuits 504 and/or other circuits(not shown) of the media player 500 may process data, perform codingand/or encryption, perform calculations, format data and/or perform anyother media player function.

The media player 500 may communicate with mass data storage 510 thatstores data such as compressed audio and/or video content in anonvolatile manner. In some implementations, the compressed audio filesinclude files that are compliant with MP3 format or other suitablecompressed audio and/or video formats. The mass data storage may includeoptical and/or magnetic storage devices for example hard disk drives HDDand/or DVDs. At least one HDD may have the configuration shown in FIG.17A and/or at least one DVD may have the configuration shown in FIG.17B. The HDD may be a mini HDD that includes one or more platters havinga diameter that is smaller than approximately 1.8″. The media player 500may be connected to memory 514 such as RAM, ROM, low latency nonvolatilememory such as flash memory and/or other suitable electronic datastorage. The media player 500 also may support connections with a WLANvia a WLAN network interface 516. Still other implementations inaddition to those described above are contemplated.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

1. A digital-to-analog converter (DAC), comprising: a capacitive DACthat comprises: N first capacitances that are connected in parallel andthat have first ends and second ends, wherein N is an integer greaterthan one; and N first switches that selectively connect a selected oneof said second ends of said N first capacitances to a common node andnon-selected ones of said second ends of said N first capacitances toone of a voltage potential and a reference potential, whereincapacitance values of said N first capacitances are substantially equal;and a second DAC that communicates with said common node.
 2. The DAC ofclaim 1 wherein said DAC converts an N bit digital word into an analogoutput signal.
 3. The DAC of claim 1 further comprising: an amplifierhaving an input and an output; a feedback capacitance that communicateswith said input and said output of said amplifier, wherein said firstends of said N first capacitances communicate with said referencepotential during a first phase of said first capacitive DAC, and whereinsaid input of said amplifier selectively communicates with said firstends of said N first capacitances during a second phase of said firstcapacitive DAC.
 4. The DAC of claim 1 further comprising: an amplifierhaving an input and an output, wherein said first ends of said N firstcapacitances communicate with said reference potential during a firstphase of said first capacitive DAC, wherein said input of said amplifierselectively communicates with said first ends of said N firstcapacitances during a second phase of said first capacitive DAC, andwherein said second ends of said of said N first capacitancescommunicate with said output of said amplifier during said second phaseof said first capacitive DAC.
 5. The DAC of claim 1 wherein said secondDAC comprises a resistive DAC.
 6. The DAC of claim 5 wherein saidresistive DAC comprises: N resistances connected in series between saidvoltage reference and said reference potential; N nodes between selectones of said N resistances and said reference potential; and N secondswitches that selectively connect said common node to one of said Nnodes.
 7. The DAC of claim 1 wherein said DAC is inherently monotonic.8. The DAC of claim 1 further comprising a control module thatselectively generates switching signals to control said N first switchesand said second DAC.
 9. A successive approximation analog-to-digitalconverter comprising the DAC of claim
 1. 10. The successiveapproximation analog-to-digital converter of claim 9 further comprising:an amplifier having an input that selectively communicates with saidfirst capacitive DAC; a successive approximation module thatcommunicates with an output of said amplifier; a decoding module thatcommunicates with an output of said successive approximation module andthat selectively generates switching signals for said N first switchesand said second DAC.
 11. The DAC of claim 1 wherein said second DACcomprises a second capacitive DAC.
 12. The DAC of claim 11 wherein saidsecond capacitive DAC comprises: an amplifier having an input and anoutput that communicates with said common node; N second capacitancesconnected in parallel and having first ends and second ends, whereinsaid first ends selectively communicate with a reference potentialduring a first phase of said second capacitive DAC and wherein saidfirst ends selectively communicate with said input of said amplifierduring a second phase of said second capacitive DAC; and N secondswitches that selectively connect said second ends of said N secondcapacitances to one of said voltage reference and said referencepotential during said first phase of said second capacitive DAC and thatselectively connect said second ends of said N second capacitances tosaid output during said second phase of said second capacitive DAC. 13.The DAC of claim 12 wherein said first and second phases of said firstcapacitive DAC are non-overlapping with respect to said first and secondphases of said second capacitive DAC.
 14. The DAC of claim 12 whereinsaid first phase of said first capacitive DAC at least partiallyoverlaps said second phase of said second capacitive DAC.
 15. Adigital-to-analog converter (DAC), comprising: first converting meansfor converting a digital signal to an analog signal and that comprises:N first capacitance means for providing capacitance that are connectedin parallel and that have first ends and second ends, wherein N is aninteger greater than one; and N first switching means for selectivelyconnecting one of said second ends of said N first capacitance means toa common node and others of said second ends to one of a voltagepotential and a reference potential, wherein capacitance values of saidN first capacitance means are substantially equal; and second convertingmeans for converting a digital signal to an analog signal and thatcommunicates with said common node.
 16. The DAC of claim 15 wherein saidDAC converts an N bit digital word into an analog output signal.
 17. TheDAC of claim 15 further comprising: amplifying means for amplifying andhaving an input and an output; feedback capacitance means for providingcapacitance and that communicates with said input and said output ofsaid amplifying means, wherein said first ends of said N firstcapacitance means communicate with said reference potential during afirst phase of said first converting means, and wherein said input ofsaid amplifying means selectively communicates with said first ends ofsaid N first capacitance means during a second phase of said firstconverting means.
 18. The DAC of claim 15 further comprising: amplifyingmeans for amplifying having an input and an output, wherein said firstends of said N first capacitance means communicate with said referencepotential during a first phase of said first converting means, whereinsaid input of said amplifying means selectively communicates with saidfirst ends of said N first capacitance means during a second phase ofsaid first converting means, and wherein said second ends of said ofsaid N first capacitance means communicate with said output of saidamplifying means during said second phase of said first convertingmeans.
 19. The DAC of claim 15 wherein said second converting meanscomprises resistive converting means for converting a digital signal toan analog signal.
 20. The DAC of claim 19 wherein said resistiveconverting means comprises: N resistance means for providing resistanceand that are connected in series between said voltage reference and saidreference potential; N nodes between select ones of said N resistancemeans and said reference potential; and N second switching means forselectively connecting said common node to one of said N nodes.
 21. TheDAC of claim 15 wherein said converting means is inherently monotonic.22. The DAC of claim 15 further comprising control means for selectivelygenerating switching signals to control said N first switching means andsaid second converting means.
 23. A successive approximationanalog-to-digital converter comprising the DAC of claim
 15. 24. Thesuccessive approximation analog-to-digital converter of claim 23 furthercomprising: amplifying means for amplifying and for selectivelycommunicating with said first converting means; approximating means forsuccessively approximating and for communicating with an output of saidamplifying means; decoding means for communicating with an output ofsaid successive approximating means and for selectively generatingswitching signals for said N first switching means and said secondconverting means.
 25. The DAC of claim 15 wherein said second convertingmeans comprises capacitive converting means for converting a digitalsignal to an analog signal.
 26. The DAC of claim 15 wherein said secondcapacitive DAC comprises: amplifying means for amplifying having aninput and an output that communicates with said common node; N secondcapacitance means for providing capacitance, that are connected inparallel and that have first ends and second ends, wherein said firstends selectively communicate with a reference potential during a firstphase of said second capacitive converting means and with said input ofsaid amplifying means during a second phase of said second capacitiveconverting means; and N second switching means for selectivelyconnecting said second ends of said N second capacitance means to one ofsaid voltage reference and said reference potential during said firstphase of said second capacitive converting means and that selectivelyconnect said second ends of said N second capacitance means to saidoutput of said amplifying means during said second phase of said secondcapacitive converting means.
 27. The DAC of claim 26 wherein said firstand second phases of said first converting means are non-overlappingwith respect to said first and second phases of said second convertingmeans.
 28. The DAC of claim 26 wherein said first phase of said firstconverting means at least partially overlaps said second phase of saidsecond converting means.
 29. A method for providing a digital-to-analogconverter (DAC), comprising: connecting N first capacitances of a firstcapacitive DAC in parallel, wherein said N first capacitances have firstends and second ends, N is an integer greater than one, and capacitancevalues of said N first capacitances are substantially equal; selectivelyconnecting a selected one of said second ends of said N firstcapacitances to a common node; selectively connecting others of saidsecond ends to one of a voltage potential and a reference potential; andconnecting a second DAC to said common node.
 30. The method of claim 29further comprising converting an N bit digital word into an analogoutput signal.
 31. The method of claim 29 further comprising selectivelysampling and holding an output of said DAC.
 32. The method of claim 29further comprising selectively sampling and integrating an output ofsaid DAC.
 33. The method of claim 29 further comprising implementingsaid second DAC using a resistive DAC.
 34. The method of claim 29further comprising: connecting N resistances of said resistive DAC inseries between said voltage and reference potentials; providing N nodesbetween select ones of said N resistances and said reference potential;and selectively connecting said common node to one of said N nodes. 35.The method of claim 29 wherein said DAC is inherently monotonic.
 36. Themethod of claim 29 further comprising selectively generating switchingsignals to control said N first switches and said second DAC.
 37. Themethod of claim 29 further comprising: successively approximating aninput signal; selectively generating switching signals for said N firstswitches and said second DAC based on said successive approximating. 38.The method of claim 29 wherein said second DAC comprises a capacitiveDAC.
 39. The method of claim 38 further comprising: connecting N secondcapacitances of a second capacitive DAC in parallel, wherein said Nsecond capacitances have first ends and second ends; selectivelyconnecting said first ends with a reference potential during a firstphase of said second capacitive DAC; selectively connecting said firstends with an input of an amplifier during a second phase of said secondcapacitive DAC; selectively connecting said second ends of said N secondcapacitances to one of said voltage reference and said referencepotential during said first phase of said second capacitive DAC; andselectively connecting said second ends of said N second capacitances tosaid output of said amplifier during said second phase of said secondcapacitive DAC.
 40. The DAC of claim 39 wherein said first and secondphases of said first capacitive DAC are non-overlapping with respect tosaid first and second phases of said second capacitive DAC.
 41. The DACof claim 39 wherein said first phase of said first capacitive DAC atleast partially overlaps said second phase of said second capacitiveDAC.